38mm Schwalbe Pro One

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barrows wrote:

Umm...  25 mm internal width road rims are common, and are designed for best performance with 28-30 mm tires!  See Enve or Zipp's latest aero wheels for road racing, used by many in the pro peloton with 28 mm tires.

best AERO performance. Has little to nothing to do with the handling performance, which IME is crap. I am barely OK with the handling of a 38mm tire on a 25mm rim. 

Volsung wrote:Someone stop Shiggy from finding out about fat bikes.

same thing applies. I like fat bikes as rock crawlers.
If I am not on deep snow or sand I use 65mm (external) rims with 4.0-4.5” tires.
the times I have used 80mm (external) rims on trails I have pinch flatted on rocks that were no problem with the same tires at the same pressures on the narrower rims. And the snake bite cuts in the tubes were only 15mm apart. 

stu wrote:I agree the tires feel firmer both radially and laterally on a wider rim but I've never used pressures anywhere near low enough to risk casing collapse in cornering.  I think that's more likely to be an issue with really narrow rims, like 1/3 of the tire width.

 

stu wrote:The 2022 ETRTO standards allow down to a 28 mm tire on a 25 mm rim, only 12% wider than the rim.  I suppose that's safe, as in not likely to blow off, but I wouldn't ride that combination on anything much rougher than a velodrome.  On pavement I've had good results with tires between 40% and 80% wider than the rim.  Off road everything is different, I'd say 80% wider than the rim is more like a minimum.

I forgot to mention most of my experience is with tires having slick or nearly slick treads.  Those have a round profile with just about any rim width though the radius may vary.  For any tire with significant tread I'd follow the tire maker's rim recommendation.

 

The new ETRTO  specs are more about safety than performance. 

When I say round profile it is more about the sidewall shape, not the tread. O or C rather than U. My experience is in-line with this explanation and has been since the early ‘90s:
https://www.renehersecycles.com/myth-18-wide-tires-need-wide-rims

I even rode trails with 2.5” tires on 13mm rims at 15psi. Was squirrely on hard surfaces unless raised it to about 28psi.
Did a lot of trail riding on 26x1.5 (38mm) tires and went to ~15mm rims from 22 to reduce pinch flats. It worked.

On the other extreme, I did try a 26x1.25 slick on 65mm (external, ~59 internal). It actually seated and was “rideable”. I would bang the rim itself on the ground in corners while rolling the tire sidewall.  Normal lean angles impossible without the tire losing contact with the ground. 

shiggy wrote:

The new ETRTO  specs are more about safety than performance.
When I say round profile it is more about the sidewall shape, not the tread. O or C rather than U.

I just took a closer look at my 34 mm tires (measuring 35.5 mm) on 25 mm rims.  The casings appear to be quite round with the treads peaking a bit in the center.

I even rode trails with 2.5” tires on 13mm rims at 15psi. Was squirrely on hard surfaces unless raised it to about 28psi.

I noticed very supple 48 mm tires (Soma SV) on 21 mm rims feeling a little unsteady on pavement around 30 psi.  I haven't felt that with 25 mm rims.  But as you say more pressure has the same effect. 

Did a lot of trail riding on 26x1.5 (38mm) tires and went to ~15mm rims from 22 to reduce pinch flats. It worked.

In more than 50 years I've had only one pinch flat, that from hitting a pothole with a 28 mm tire on a 13 mm rim at about 60 psi.  But in the last two months ago my daughter and I have both destroyed car tires by hitting potholes.  My conclusion is potholes are bad for tires.  🙂

On the other extreme, I did try a 26x1.25 slick on 65mm (external, ~59 internal). It actually seated and was “rideable”. I would bang the rim itself on the ground in corners while rolling the tire sidewall.  Normal lean angles impossible without the tire losing contact with the ground.

My 34 mm tires on 25 mm rims contact smooth pavement on the tread beyond lean angles I would ever attempt.  But a narrower rim would sit farther from the road and be better protected from impacts due to surface roughness.

shiggy wrote:
best AERO performance. Has little to nothing to do with the handling performance, which IME is crap. I am barely OK with the handling of a 38mm tire on a 25mm rim. 

That is pure nonsense.  Plenty of World Tour pros are riding these set ups down quite challenging descents, at very high speeds.

barrows wrote:

That is pure nonsense.  Plenty of World Tour pros are riding these set ups down quite challenging descents, at very high speeds.

The widest Roval road rim is 21mm. Enve and Zipp, 23mm.
Road pros ride what they are told to, and have skills that can compensate for the deficiencies to have gains on other areas. Riding deep section rims on fast descents with gusty crosswinds have given me even more respect for the pros’ skills  

I am not saying the narrow tires on wide rims can not be ridden on difficult descents, just that they are not the best handling combination, and a combination I have ZERO desire to ever use again. 

shiggy wrote:
The widest Roval road rim is 21mm. Enve and Zipp, 23mm.
Road pros ride what they are told to, and have skills that can compensate for the deficiencies to have gains on other areas. Riding deep section rims on fast descents with gusty crosswinds have given me even more respect for the pros’ skills  

 

I am not saying the narrow tires on wide rims can not be ridden on difficult descents, just that they are not the best handling combination, and a combination I have ZERO desire to ever use again. 

Incorrect: Enve SES series rims are 25 mm internal, as are Zipp 303 Firecrest.  Both are widely used by road racers with 28 mm tires.  These rims are available in a variety of depths to suit conditions.

I think one of the things you have to be able to do is separate what makes sense from an engineering perspective vs a marketing perspective.  The rims have to keep getting wider every year so that people will buy new ones.  Marketing departments want you to think 21mm rims are too narrow for road tires so you’ll buy the 23mm.  Then next year they come out with 25mm so you’ll ditch the 23 and buy the 25.  Then the following year they’ll be 27mm.  Just because you can stick a 23mm tire on a 30mm rim and now it measure 30mm does not mean you get the same benefits as an actual 30mm tire on a 21mm rim.  And the whole “the pros are doing it argument” is and has always been a weak argument.  Pros used to ride 20mm tires at 130psi because they claimed narrower tires pumped to their maximum are faster.  Thankfully that “pro wisdom” has been proven wrong and put to rest.  

barrows wrote:

Incorrect: Enve SES series rims are 25 mm internal, as are Zipp 303 Firecrest.  Both are widely used by road racers with 28 mm tires.  These rims are available in a variety of depths to suit conditions.

OK, I didn’t check every model.
The SES models range from 21 to 25  https://www.enve.com/product-category/wheels/
Zipp from 19 to 25  https://www.sram.com/en/zipp/road/ride-style/road-race?filters=&sort=Relevancy&page=1
and of course that assumes the pros are riding clinchers/tubeless ready. Some are still using tubulars, which are always round cross sections.

Still, from Cyclingnews on the 2023 team equipment article:
”The bigger - or best-funded - teams can enjoy selecting all of their equipment purely based on performance advantages. Even choosing equipment off the back of their own independent testing. UAE Team Emirates for instance will be racing on Enve wheels for 2023 after testing the top brands at the Milan Polytechnic wind tunnel and deciding on the American manufacturer.”
A choice made mainly on aerodynamic performance, not handling performance of the fitted tires.